powerpc/nvram: Improve partition removal

Existing code is nasty, has bugs etc... rewrite the function
more simply, and make it take the signature and optional
name of the partitions to remove as arguments, thus making
it a more generic utility.

We also try to remove a log partition that we find and is too
small rather than creating a duplicate.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/nvram_64.c

@@ -247,61 +247,54 @@ static unsigned char __init nvram_checksum(struct nvram_header *p)
 	return c_sum;
 }
 
-static int __init nvram_remove_os_partition(void)
+/**
+ * nvram_remove_partition - Remove one or more partitions in nvram
+ * @name: name of the partition to remove, or NULL for a
+ *        signature only match
+ * @sig: signature of the partition(s) to remove
+ */
+
+static int __init nvram_remove_partition(const char *name, int sig)
 {
-	struct list_head *i;
-	struct list_head *j;
-	struct nvram_partition * part;
-	struct nvram_partition * cur_part;
+	struct nvram_partition *part, *prev, *tmp;
 	int rc;
 
-	list_for_each(i, &nvram_part->partition) {
-		part = list_entry(i, struct nvram_partition, partition);
-		if (part->header.signature != NVRAM_SIG_OS)
+	list_for_each_entry(part, &nvram_part->partition, partition) {
+		if (part->header.signature != sig)
 			continue;
-		
-		/* Make os partition a free partition */
+		if (name && strncmp(name, part->header.name, 12))
+			continue;
+
+		/* Make partition a free partition */
 		part->header.signature = NVRAM_SIG_FREE;
 		sprintf(part->header.name, "wwwwwwwwwwww");
 		part->header.checksum = nvram_checksum(&part->header);
-
-		/* Merge contiguous free partitions backwards */
-		list_for_each_prev(j, &part->partition) {
-			cur_part = list_entry(j, struct nvram_partition, partition);
-			if (cur_part == nvram_part || cur_part->header.signature != NVRAM_SIG_FREE) {
-				break;
-			}
-			
-			part->header.length += cur_part->header.length;
-			part->header.checksum = nvram_checksum(&part->header);
-			part->index = cur_part->index;
-
-			list_del(&cur_part->partition);
-			kfree(cur_part);
-			j = &part->partition; /* fixup our loop */
-		}
-		
-		/* Merge contiguous free partitions forwards */
-		list_for_each(j, &part->partition) {
-			cur_part = list_entry(j, struct nvram_partition, partition);
-			if (cur_part == nvram_part || cur_part->header.signature != NVRAM_SIG_FREE) {
-				break;
-			}
-
-			part->header.length += cur_part->header.length;
-			part->header.checksum = nvram_checksum(&part->header);
-
-			list_del(&cur_part->partition);
-			kfree(cur_part);
-			j = &part->partition; /* fixup our loop */
-		}
-		
 		rc = nvram_write_header(part);
 		if (rc <= 0) {
-			printk(KERN_ERR "nvram_remove_os_partition: nvram_write failed (%d)\n", rc);
+			printk(KERN_ERR "nvram_remove_partition: nvram_write failed (%d)\n", rc);
 			return rc;
 		}
+	}
 
+	/* Merge contiguous ones */
+	prev = NULL;
+	list_for_each_entry_safe(part, tmp, &nvram_part->partition, partition) {
+		if (part->header.signature != NVRAM_SIG_FREE) {
+			prev = NULL;
+			continue;
+		}
+		if (prev) {
+			prev->header.length += part->header.length;
+			prev->header.checksum = nvram_checksum(&part->header);
+			rc = nvram_write_header(part);
+			if (rc <= 0) {
+				printk(KERN_ERR "nvram_remove_partition: nvram_write failed (%d)\n", rc);
+				return rc;
+			}
+			list_del(&part->partition);
+			kfree(part);
+		} else
+			prev = part;
 	}
 	
 	return 0;
@@ -484,17 +477,19 @@ static int __init nvram_setup_partition(void)
 						NVRAM_BLOCK_LEN) - sizeof(struct err_log_info);
 			return 0;
 		}
+
+		/* Found one but it's too small, remove it */
+		nvram_remove_partition("ppc64,linux", NVRAM_SIG_OS);
 	}
 	
 	/* try creating a partition with the free space we have */
 	rc = nvram_create_partition("ppc64,linux", NVRAM_SIG_OS,
 				       NVRAM_MAX_REQ, NVRAM_MIN_REQ);
 	if (rc < 0) {
-		/* need to free up some space */
-		rc = nvram_remove_os_partition();
-		if (rc)
-			return rc;	
-		/* create a partition in this new space */
+		/* need to free up some space, remove any "OS" partition */
+		nvram_remove_partition(NULL, NVRAM_SIG_OS);
+	
+		/* Try again */
 		rc = nvram_create_partition("ppc64,linux", NVRAM_SIG_OS,
 					    NVRAM_MAX_REQ, NVRAM_MIN_REQ);
 		if (rc < 0) {